Sandblast shaping



May 2, 1939. R KNOX 2,156,696

SANDBLAST SHAPING Filed Aug. 25, 1957 A In van tar; ort fza.

Patented May 2, 1939 erro sms-s SANDBLAST SHAPING Robert Knox, Berlin,

Vt., assignor to `Tones Brothers Company, Boston, Mass., a corporation of Maine Application August 25,

3 Claims.

This invention relates to the art of shaping or otherwise ornamenting various kinds of surfaces by sand-blasting (with suitable abrasive not necessarily sand) selected areas of the surn faces through openings in elastic sheet material applied to the surface. In some cases the material is applied to the surface in liquid form, allowed to set and then cut away throughout selected areas to expose the surface through the cut-away portions. In other cases a mask is first made in the form of a sheet of soft rubber with openings therethrough and cemented to the face of the material to be blasted.

While the aforesaid methods are quite satisfactory for certain kinds of simple design they are limited in application. For example, it is frequently desirable to form a design having two different kinds of ornamentation with the areas of one kind interspersed among the areas of the other kind. Thus in forming designs on monuments and the like it is sometimes desirable to form a design having deep cuts into the stone distinctly to outline the Various portions of the design and then to shape the outlined portions by cutting them out more or less depending upon the particular design. While the aforesaid methods are capable of outlining the various portions of such designs they have been incapable of use for both outlining and shaping the outlined portions.

The objects of the present invention are to provide method and means for readily forming designs in which interspersed areas are differently shaped or treated by sand-blasting, to obtain sharp edges between the interspersed area of different shape, and generally to improve the art of ornamentation by sand-blasting methods.

Foi` the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which,

Figs. 1 and 2 are complemental masks;

Fig. 3 is a section on line 3-3 of Fig. 1 showing the mask applied to a slab of stone;

Fig. 4 is a section on line 4--4 of Fig. 2 showing the mask applied to a slab of stone; and

Fig. 5 is an elevation of a piece of stone shaped according to the present invention.

In one aspect the present invention comprises a pair of complemental masks such as shown at I and 2 in Figs. 1 and 2. The mask I has openings 3 shaped and spaced in accordance with the desired design and the mask 2 has openings 4 which are complemental to the openings of mask I, in the sense that when the two masks 55 are superposed the solid parts of one mask cover 1937, serial No. 160,801

all or parts of the openings in the other mask, and the solid parts of the latter mask cover all or parts of the openings in the first mask.

The masks I and 2 'are preferably formed of soft rubber by a molding process which involves 5 cutting recesses in a plate of Bakelite or the like and then pouring the rubber mix into the recesses. After the recesses are filled the rubber is allowed to set. The recesses in the molds are curved in cross-section so that the molded article l0 can readily be removed from the mold. For use in forming the masks a suitable material comprises vulcanized liquid latex which sets quickly after it is poured into the molds and produces a soft pliable mask. In using the masks 15 the side which was uppermost in the molds is applied to the surface of the stone and is temporarily cemented thereto during the blasting operation.

A typical use of the masks I and 2 is illus- 20 trated in Figs. 3 and 4. In Fig. 3 the mask I hasl been cemented to a slab of stone 5 and concave recesses 6 have been formed in the upper face of the stone by sand-blasting through the openings 3 in the mask. By using a ne jet of abrasive 25 these recesses may be etched deeper in the middle than around their margins so that the recesses are concave in both dimensions of the etched areas. After the recesses B have been formed in the surface of the stone the mask I` is peeled 30 off the 4stone and the mask 2 is substituted in the same location. By virtue of the complemental character of the two masks the second mask covers the recesses 6 and exposes other areas of the stone through the opening 4. By more intensive or a more prolonged blasting through the opening 4 deeper portions 'I are than cut in the stone, after which the mask 2 is removed.

In applying each mask to the stone the underneath surface of the mask is cemented, preferably with rubber cement, to the stone, preferably throughout the entire area of the surface.

As shown in Fig. 4 the second mask is pressed into the concave recesses formed in the first shaping operation ;A otherwise the edges of the deeper re- 45 cesses formed in the second blasting operations would not be sharp. After the second mask is peeled off the stone is washed with naphthol to remove the rubber cement adhering to the stone, and if desired the stone may be similarly washed after peeling off the first mask.

Fig. 5 shows the finished product in which the deeper portions 'I present dark shadows and the shallow portions 6 present lighter shadows.

By employing a thin, soft, elastic mask, formed of vulcanized latex or the like, the second mask may be easily pressed into the recesses formed in the ,first shaping operation, thereby conforming to the contour of the stone as shaped in the rst operation; and by cementing the second mask in the recesses the peripheries of the openings in the second mask are held snugly against the stone, thereby preventing abrasive particles from impinging on those portions of the recesses which are not to be further shaped in the second operation and also preventing particles from accumulating in these recesses under the solid portions of the second mask. As a result the edges of the stone between the areas blasted in the iirst operation and the areas blasted in the second operation are sharply defined.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modiiiications and equivalents which fall within the scope of the appendedr claims.

I claim:

1.' The method of differently treating diierent groups of areas of an article bysand-blasting i through masks, which comprises blasting one of said groups of areas through one mask to etch recesses in the article which are concave in both dimensions of the areas, then covering the blasted areas With a soft elastic mask complemental to the rst mask, pressing the soft mask into said recesses and cementing it therein, and differently shaping another group of areas by blasting through the openings in the second mask.

2. The method of shaping the surface of an article by sand-blasting through masks having openings therein, characterized by first blasting the surface through the openings in a mask to form in certain portions recesses which are concave in both dimensions of the surface, with unblasted areas therebetween, then covering said certain portions with a soft elastic mask, pressing the soft mask into said recesses and cementing it therein, and nally blasting through the openings inthe second mask to form grooves in said areas.

3. The method of shaping the surface of an article which comprises protecting thesurfa'ce with a layer of protective material having openings corresponding to one group of areas, blasting through said openings to form in said surface recesses which are concave in both dimensions of the surface, removing said layer, applying to the surface a soft elastic mask having a design corresponding to the blasted areas and having openings over other areas of said surface, pressing the soft elastic mask into said concave re'- cesses and cementing it therein, shaping said other areas by blasting through the openings of said mask, and then peeling oi said mask.

` ROBERT KNOX. 

